Be honest about your abilities and your passion for the subject, include work that shows you are able to communicate a story clearly and creatively, and don’t be afraid to ask them questions about their project and aims! Show a true interest in the work and their history (research what they’ve done before- it’ll really make a difference in conversation and shows you give a damn), and yeah just be chill and keep in mind that even if you don’t get the job if you make a strong, positive impression they’ll remember you and be more likely to consider you in the future. Sometimes people don’t get the job but the applicant that does has to drop out for some reason, so there’s always a chance you’ll get a call from them again if you rock it. Best of luck!